The present invention relates generally to fire protection sprinkler systems, and more particularly, to a cover plate for a concealed fire sprinkler head.
Sprinkler heads have long been used in automatic fire extinguishing systems in order to controllably disperse a fluid in order to suppress or extinguish a fire in a designated area. Typically, the fluid utilized in automatic fire extinguishing systems is water, however, systems have also been advanced to disperse other fire extinguishing fluids. In one common design, sprinkler heads include a solid metal base with a central orifice having an inlet connected to a pressurized supply of water or other fire extinguishing fluid. A deflector, spaced from the sprinkler body, alters the trajectory of the water in an optimum pattern when discharged from the central orifice. In many conventional sprinkler heads, the deflector is fixedly spaced from the outlet by a pair of rigid arms and mounted on a boss joining the arms. A thermally sensitive trigger assembly is positioned between the deflector, boss and the central orifice outlet and sealingly engages a sealing assembly, which under non-activated conditions, prohibits water flow from the outlet. When the temperature reaches a preselected value indicative of a fire, the trigger assembly releases the sealing member and permits the expulsion of water from the outlet.
In another common design, often referred to in the industry as a concealed, recessed or flush sprinkler head, the structure in which the sprinkler body is positioned has a recess or cavity, sized to enable the insertion of the sprinkler body. The deflector is movably supported proximate to the outlet, with in a cavity formed in the sprinkler body. A housing is attached to, and extends beyond the bottom region of the sprinkler body and includes an annular flange positioned about the exterior perimeter of the cavity in which the sprinkler body is located. A sealing assembly, located within the interior of the sprinkler body, seals the outlet of the sprinkler body and is maintained in a closed position by a pair of pins or actuators depending from the bottom of the sprinkler body. The pins are held in an inwardly biased or closed position by a thermally sensitive trigger assembly, positioned between the sprinkler body and the bottom of the housing, which is thermally responsive in the temperature range indicative of a fire. Under normal temperatures, the presence of the thermally sensitive trigger assembly prohibits fluid flow through the central orifice. When the temperature within the designated area rises to a preselected value due to the presence of fire, the thermally sensitive trigger assembly fuses, or ruptures, causing the pins to move in an outward direction, and in consequence, results in the movement of the deflector away from the outlet of the sprinkler body, with its movement halted a preselected distance within the interior of the designated area. Activation of the thermally sensitive trigger assembly also releases the sealing assembly, enabling pressurized fluid to travel through the sprinkler body and be expelled therefrom. Once expelled from the outlet, the fluid impacts the deflector, and its trajectory is altered in an optimum pattern.
Concealed sprinkler heads are commonly equipped with a concealing cover plate which is coupled to the housing. When the deflector is expelled from the housing, it dislodges the cover plate, causing its motion away from the sprinkler head. Under normal conditions, the cover plate conceals the interior of the sprinkler body from view, and in most instances, completely encloses the bottom of the housing.
As the thermally sensitive trigger assembly in a concealed sprinkler is normally positioned above the annular flange, or, at least co-planar therewith, the presence of a cover plate reduces the air flow received by the thermally sensitive trigger assembly. As the air flow rate impacting the thermally sensitive trigger assembly is reduced, the heat transfer rate to the thermally sensitive trigger assembly also decreases. In consequence of the reduced air flow rate, the thermally sensitive trigger assembly is elevated to the preselected activation temperature at a slower rate, and reduces the response time of the sprinkler head.
In response to slow activation times, cover plates have been provided with a plurality of central openings or slots, often formed in surfaces projecting from the center of the cover plate, to permit the heat to pass therethrough and impact the thermally sensitive trigger assembly. These airway openings, however, draw attention to the cover plate and diminish the cover plate's ability to perform its function of providing an aesthetic cover that does not visually detract from the ceiling or sidewall in which the sprinkler head is positioned.
Consequently, there is a need for a cover plate which conceals the sprinkler head interior, provides an aesthetic, low profile cover, permits heat to be directed to the thermally responsive trigger assembly, and is configured to be immediately and effectively dislodged from the housing in response to a fire.